ANNIVERSARY ADDRESS OF THE PRESIDENT. 



Ixvii 



containing Cardita crenata (Goldf.), Aviculce of the family of the 

 Gryphseatse, and small turreted shells. Below these are thick 

 masses of dolomite, which are again underlaid by sandstones with 

 impressions of Keuper plants. The Gervillia-beds also occur in the 

 vicinity of the Lake of Como, forming a good geological horizon 

 below the Lias. The author states that they have given the name of 

 San Casciano formation to the whole series of beds situated between 

 the Keuper and the Lias. It is a marine formation which appears 

 to be wanting in the North of Europe, and is only developed in the 

 Alpine chain and in Eastern Europe. In a palseontological point of 

 view it is distinguished from the overlying Lias by the absence of 

 Belemnites, and from the Trias on which it reposes by the occurrence 

 of Ammonites a cloisons persillees. 



After alluding to the previous erroneous opinions entertained by 

 various geologists respecting the position of the Dachstein Limestone 

 and the Gervillia beds. Prof. Merian observes that the Austrian geo- 

 logists are now of the same opinion as himself and his friend respecting 

 the order of superposition of these beds. The only difference is that 

 the former wish to refer these two groups to the lower Lias, whilst 

 he and M. Escher refer the beds with Ammonites globosus and the 

 beds of S. Casciano to a separate formation, which they call Upper 

 Muschelkalk, In the communication read at Gottingen the Pro- 

 fessor repeated these arguments, adding that the S. Casciano beds 

 below the Dolomite alternate in some spots with some of the Keuper 

 beds, and particularly with the Letten coal beds ; and that he considers 

 that the whole formation, which is essentially marine, should be looked 

 on as a marine Keuper in the East and South of Europe, correspond- 

 ing with or equivalent to the land or terrestrial Keuper of the West, — 

 that they are in fact the marine representatives of the Keuper*. 



It is perhaps one of the most interesting features in the considera- 

 tion of this question, and one which has added greatly to the difficulty 

 of unravelling the true relations of this part of Alpine geology, that 

 we here find a regular unbroken sequence of beds lying conformably 

 one over the other, from the lowest member of the Triassic group 

 into the Liassic and the Jurassic formations. Not only do the dif- 

 ferent beds of sandstone, shales, limestones, and dolomites pass into 

 and sometimes even alternate with each other, thereby producing 

 what may be almost called an inosculation of the strata, but we 

 also find a gradual passage of organic forms from one formation to 

 another. If each new successive stratum as we ascend presents us 

 with new groups and new associations of organic life, we still find 

 them accompanied by some of the forms which characterized the 

 beds below. Thus, while on geognostical and mineralogical grounds 

 we are prevented from drawing very exact lines of demarcation be- 

 tween one formation and another, we are equally debarred, on palae- 

 ontological grounds also, from defining with absolute accuracy or 

 correctness the respective limits of the different groups. The Keu- 



* For further details see also a Memoir by M. A. Escher von der Linth on the 

 Geology of the Vorarlberg, published in the thirteenth volume of the Memoires 

 de la Societe Helvetique des Sciences Naturelles, 1853. 



